Safe Haskell | None |
---|---|
Language | Haskell2010 |
This library provides generic machinery (via GHC.Generics and `generics-sop`) to encode values of some algebraic type as points in a vector space.
Processing datasets that have one or more categorical variables (which in other words are values of a sum type) typically requires a series of boilerplate transformations, and the encodeOneHot
function provided here does precisely that.
Internals
This library makes use of generic programming to analyze both values and types (see the Generics
module).
One-hot encoding
encodeOneHot :: forall a. G a => a -> OneHot Source #
Computes the one-hot encoding of a value of a sum type. A sum type is defined as a choice between N type constructors, each having zero or more fields.
The number of constructors becomes the dimensionality of the embedding space, and the constructor position (as defined in its implementation) is interpreted as the index of the nonzero coordinate.
NB : This function computes the generic representation only up to the outermost constructor (see examples below).
The type of the input value must be an instance of Generic
(from GHC.Generics) and of Generic
(from the `generics-sop` library).
> :set -XDeriveGeneric > import qualified GHC.Generics as G > import qualified Generics.SOP as SOP > import Data.Record.Encode > data X = A | B | C deriving (Enum, G.Generic) > instance SOP.Generic X
The B
constructor is the second (i.e. position 1 counting from 0) of a choice of three :
>>>
encodeOneHot B
OH {oDim = 3, oIx = 1}
The Just
constructor is the second of a choice of two:
>>>
encodeOneHot $ Just B
OH {oDim = 2, oIx = 1}
The Nothing
constructor is the first:
>>>
encodeOneHot (Nothing :: Maybe Int)
OH {oDim = 2, oIx = 0}
Types
A one-hot encoding is a d-dimensional vector having a single component equal to 1 and all others equal to 0. We represent it here compactly as two integers: an integer dimension and an index (which must both be nonnegative).
Utilities
compareOH :: OneHot -> OneHot -> Maybe Ordering Source #
Compares two one-hot encodings for equality. Returns Nothing if the operand dimensions are not equal.
>>>
compareOH (OH 3 2) (OH 3 1)
Just GT
>>>
compareOH (OH 3 2) (OH 5 1)
Nothing